Reversing valves are typically used in various systems in which a fluid is directed to flow in various alternative loops or circuits. For instance, heat pumps are specialized refrigeration systems that can be selectively configured to operate in either of two different modes. In the first mode, known as the cooling mode, energy in the form of heat is removed from an “inside” environment and transferred to an “outside” environment. Accordingly, in the second mode, known as the heating mode, heat energy is transferred into the inside environment. To convey the heat energy, the heat pump system uses a compressor to circulate fluid refrigerant through a closed system that includes heat transfer coils located in each environment. In addition to circulating the refrigerant, the compressor is used to impart heat energy into the system.
To switch the heat pump system between heating and cooling modes, the system uses a reversing valve that can be selectively manipulated to alter the flow of refrigerant. Specifically, a 4-way reversing valve can be installed which reverses the direction of refrigerant flow through the heat transfer coils. Such a reversing valve typically includes four or more separate ports through which the reversing valve is connected to the rest of the heat pump system. The first port is always in communication with the high pressure discharge of the compressor while the second port is always in communication with the low pressure inlet of the compressor. The remaining two ports, or system ports, are in communication with the heat transfer coils.
The reversing valve also includes a movable valve member that can be selectively placed into one of two alternative positions. In the first position, the valve member channels refrigerant directly between the second port communicating with the compressor inlet (“the compressor inlet port”) and one of the system ports while in the second position the valve member channels refrigerant directly between the compressor inlet port and the other system port. In addition to channeling the refrigerant directly between the compressor inlet port and either of the system ports, the valve member functions to prevent the high pressure refrigerant from the first port communicating with the compressor discharge (“the compressor discharge port”) from directly entering the compressor inlet port. Because the valve member is subject to the large pressure differential existing between the compressor discharge port and the compressor inlet port, prior art valve members are often provided with additional support structures. These support structures are typically located proximate to where the valve member encounters the compressor inlet port and may obstruct refrigerant flow resulting in an increase in the pressure drop across the reversing valve. Since the compressor must make up for the pressure drop, the overall efficiency of the heat pump system suffers.
By design, the compressor inlet port and two system ports are often arranged in a row along the exterior of the reversing valve. Accordingly, to direct refrigerant between any particular paring of the compressor inlet port and the two system ports, the valve member must channel the refrigerant through a relatively sharp bend. It is known that causing fluid to flow through a bend results in the development of turbulent secondary currents within the fluid stream. These turbulent currents cause shock and friction losses, and often require extensive lengths of relatively straight flow to dissipate. The shock and friction losses in turn add to the pressure drop across the reversing valve that must be made up for by the compressor, therefore reducing the efficiency of the heat pump system. It is also known that the magnitude of these losses is a function of the ratio between the inside and outside radiuses of the bend. Particularly, a larger difference between the inner radius and the outer radius results in a lower value of the curve ratio (inner radius/outer radius). A low valve for the curve ratio results in more pronounced turbulence and secondary flows, and accordingly increases the friction losses. However, to reduce the overall size of the reversing valve, prior art valve members typically have very small curve ratios, which accordingly degrades the efficiency of the heat pump system.